The present invention relates to heating systems for automobiles and more particularly to a hot-water type heating system which includes a radiator and a heat accumulating water tank and utilizes the cooling water of an engine as a heat source.
In the past, water-cooled engine equipped automobiles have been provided with heating systems of the hot-water type which utilize the cooling water of the water-cooled engine as a heat source to heat the interior of the vehicle compartment. This type of heating system is disadvantageous in that during the period immediately following the engine starting, the temperature of the engine cooling water is so low that the heating effect required by the vehicle occupants cannot be obtained and the driver is compelled to drive the vehicle under very cold conditions.
Conventional hot-water type heating systems of the type including a regenerative water tank in addition to the radiator are disclosed, for example, in Japanese Laid-Open Patent Publication No. 53-114140. This type of heating system further includes a heat accumulating water tank as a means of overcoming the situation in which just after the starting of the engine under winter conditions the engine cooling water temperature is so low that the heating effect required by the vehicle occupants cannot be provided by the radiator alone. Thus the high-temperature cooling water produced during the engine operation is stored and kept warm in the heat accumulating water tank so that during the period just after the engine starting where the cooling water temperature is low, the stored high-temperature water is introduced into the heating radiator and the heat energy of the high-temperature cooling water is taken out as hot air, thus providing the desired heating effect from the time just following the start of the engine operation. This type of heating system is also disadvantageous. This is so because while the desired pipe lines, electromagnetic valve and electrically-operated water pump are provided to circulate the engine cooling water only between the radiator and the heat accumulating water tank, and the temperature of the cooling water in the engine section is sensed by a water temperature sensor such that when the cooling water temperature is high the radiator and the heat accumulating water tank are connected in parallel with the engine cooling water outlet and inlet to circulate the cooling water in parallel with the radiator and the heat accumulating water tank, if the cooling water temperature is low only the stored water in the heat accumulating water tank is circulated only through the radiator and the heat accumulating water tank and no cooling water from the engine section flows via either one or both of the radiator and the heat accumulating water tank.
As a result, when the hot water in the heat accumulating water tank is delivered to the heating radiator through one of the circulating water passages between the radiator, and the heat accumulating water tank just after the start of the engine, the cold water in the radiator, which is as low as the outside air, flows into the heat accumulating water tank. Thereafter, the hot water, which was used for heating purposes and cooled, also flows into the heat accumulating water tank. As a result, even when hot water of a sufficient temperature for heating purposes is stored in the heat accumulating water tank, the temperature of the hot water will be decreased rapidly in a short period of time by the cold water flowing into the heat accumulating water tank after an actuation of the system, thus failing to provide the satisfactory heating effect.
Moreover, the heat accumulating water tank as well as the piping, electromagnetic valve, electrically operated pump, etc., in the circulating passages provided between the heat accumulating water tank and the radiator are used solely for providing heating for the vehicle occupants during the period immediately following the starting of the engine under winter conditions. No consideration is given to the problem of a warming up operation which must also be considered when starting the engine under winter conditions.